The present invention relates to a curable resin and its preparation process, and more particularly to a curable vinyl resin having hydrolyzable silyl groups at the molecular ends or side chains, which is excellent in, particularly, flexibility, solvent resistance and adhesion to organic materials and a process for preparing the same.
Japanese Unexamined Patent Publication No. 36395/1979 discloses that a hydrolyzable silyl group-containing vinyl resin has excellent curability at room temperature, adhesion to inorganic materials such as a concrete, a glass, a copper plate or aluminum and weatherability. However, the silyl group-containing vinyl resin is unsatisfactory in flexibility, solvent resistance and adhesion to organic materials. In order to improve the flexibility, solvent resistance or adhesion to organic materials, it can be considered to blend the vinyl resin with other resins. However, when blending other flexible resins with the vinyl resin for improving the flexibility of the vinyl resin, the vinyl resin with which the flexible resin is blended is poor in dryability though the flexibility can be improved. Also, when blending the vinyl resin with other solvent-resistant resins for improving the solvent resistance of the vinyl resin, the compatibility with other resins of the obtained resin mixture becomes poor.
In order to avoid the above-mentioned problems, in Japanese Unexamined Patent Publication No. 59615/1987, there is proposed a curable resin which is prepared by copolymerizing a vinyl monomer with a prepolymer, the prepolymer being prepared by Michael's addition reaction of an oligomer having in its molecule two or more acryloyloxy and/or methacryloyloxy groups with an aminosilane compound. According to the proposal, the obtained resin is excellent in flexibility since the oligomer wherein flexible segments exist is grafted onto the main chain of the vinyl resin, and is not poor in initial dryability or is not poor in compatibility with other resins, unlike the case of blending the vinyl resin with other resins.
However, since the resin has amino groups capable of promoting hydrolysis and condensation reaction of hydrolyzable silyl groups in the resin, the resin is poor in storage stability (the resin is increased in viscosity or colored during storage), and is poor in weatherability, e.g., the cured film thereof yellows.
An object of the present invention is to solve the above-mentioned defects and to provide a hydrolyzable silyl group-containing vinyl resin having excellent flexibility, solvent resistance, storage stability and adhesion to organic materials as well as the excellent curability at room temperature, adhesion to inorganic materials and weatherability.
A further object of the present invention is to provide a process for preparing such a vinyl resin.
These and other objects of the present invention will become apparent from the description hereinafter.